The present invention relates to the handling of remote sensor data of detected objects. In particular, the present invention involves a method and apparatus for matching sensor data or observations of detected objects to tracks of past object detections.
The ability to remotely sense and track target objects is useful in a wide array of military and scientific applications. Typically, remote sensing techniques may involve gathering information by using various instruments to measure electromagnetic fields, electromagnetic radiation, or acoustic energy. Remote sensing instruments may include, for example, imaging sensors, cameras, radiometers, scanners, lasers, radio frequency receivers, radar systems, sonar, thermal devices, seismographs, magnetometers, gravimeters, scintillometers, or other like instruments. Imaging sensors for remote sensing purposes include low-light-level CCD, FLIR, MMW radar, PMMW cameras, or the like.
Remote sensing is achieved with a forward looking infrared (FLIR) system by using the FLIR to detect and measure thermal or photonic energy emanating from a distant object. FLIR sensors are often used to identify, categorize, and track remote target objects. In some applications, FLIR sensors are linked to weapon systems for providing guidance input and weapon fire control.
Once an object has been detected, it may be tracked over time by linking subsequent detections of the object. To track an object, a series of sensor detections taken over a period of time must be linked to the object of interest with an acceptable amount of certainty. This may be achieved by comparing the history of past sensor detections, that is, the track of the object, to the object""s next expected orientation relative to the sensor. In this way, the most recently received sensor detection may be linked or associated with the track of an object. A detection can be positively identified as the object being tracked based on the distance between the detection and the track or expected position. This allows detections to be xe2x80x9cassociatedxe2x80x9d with the track by measuring the distance between a track-detection pair.
The processing of new detections, or observations, becomes much more complicated as the number of objects being tracked increases. The detections which are close to an expected position become candidate associations for a track. With conventional systems, this involves a comparison of each detection with every track. When there are a large number of detections (N) and tracks (M), the computational costs become prohibitively large using such conventional systems. The computational cost of associating N number of detections with M number of tracks is roughly proportional to Nxc3x97M.
The present invention satisfies a need recognized by the inventor to rapidly and efficiently associate a set of tracks with a set of observations. In accordance with the present invention, observations from various orientations are populated into a set of look-up tables which cover the three-dimensional free space directions of interest. Since nearby table entries are also nearby in position, valid track-detection pairs may be found by searching the table entries adjacent an expected position. Because a cell which is adjacent the expected cell may fall in the next table, the edges of the tables are extended to include overlap boundary edges having cells which are redundant to the adjacent table. In this way, all the cells of interest surrounding an expected cell can be searched by looking in one table. Association of a set of tracks with a set of observations is made more efficient sing the look-up table method in accordance with the present invention.
One advantage of the present invention is that the efficiencies realized in the resultant processor load become roughly linear in proportion to N+M, rather than being proportional to Nxc3x97M as with conventional systems. By using the present invention, the computational burden decreases by a factor of approximately N, which may result in a magnitude or more in throughput. By reducing the computational load of track-detection association, the present invention enables lower cost, smaller sized, less complex hardware to be used. The present invention may be used with any detection and tracking system which has a large track load and high update rates.
A preferred embodiment of the present invention associates a number of observation data tracks with the observations from a sensor such as a laser radar. This is achieved by having a plurality of tables which each have cells for storing data of said sensor observation. Each of the tables is correlated to a portion of a geometric surface, and each of the tables has rows of overlap boundary cells along one or more of the edges of the table. The overlap boundary cells contain data which is redundant to the adjacent cells of the adjoining table. The sensor observation data is stored in the appropriate table. Data that is stored near the edge of a table will also be redundantly stored in the overlap boundary cells of the adjoining table. A predicted location for each track is calculated in one of the tables, and the table cell and surrounding cells are searched. The observation data track is associated with a sensor observation if the sensor observation is within the predicted cell or in the surrounding cells.